1. Technical Field
The present invention relates to a medical and surgical method and apparatus for the correction of injuries and disorders of the musculoskeletal system in general and contractures of joints in particular. More particularly this invention relates to a dynamic orthopedic device designed to increase the range of motion of joints suffering from contractures particularly the small joints of the hand.
2. Related Art
Skeletal joint contractures often result from trauma, including fractures and dislocations of joints. In addition, bums and their scar contracture reduce the range of motion of joints. Contractures also result from muscle imbalance across joints secondary to diseases such as leprosy. Dupuytren""s disease commonly causes flexion contractures of the small joints of the hand. However, contractures can be flexion or extension contractures and can occur in any skeletal joint.
Traditionally, these injuries have been treated with various different modalities including splinting, serial plaster casts, and surgical release. Recently, significant innovations have resulted in more effective dynamic methods of treating such injuries in certain joints. For example, U.S. Pat. No. 5,376,091 to Hotchkiss et al., incorporated herein by reference, describes a dynamic finger joint support that has a proven clinical record of successful treatment of contractures. The Hotchkiss device is designed to allow, for example, the proximal interphalangeal (PIP) joint to be flexed and extended by a continuous passive motion machine that applies torque to the joint. Such flexion and extension is known to help overcome joint contractures so that the patient is often able to regain the full range of motion in the affected joint.
A deficiency of some prior art devices, generally referred to as hand splints, is that the torque required to increase the range of motion of the joint, can only be applied to the joint through the skin overlying the skeletal segments extending from either side of the joint. In addition, the force required to increase the range of motion of a joint needs to be applied for a significant amount of time. If the force is transmitted to the skeleton indirectly through the skin, the force compromises the circulation of the skin causing it to become tender, red and inflamed. In severe cases, particularly those with compromised sensation, ulcers may develop. As shown in FIGS. 1 and 2, the Hotchkiss device 5 avoids this problem for the distal interphalangeal (DIP) joint 10 by applying force directly to both the middle phalanx 12 and the distal phalanx 14. From the top view provided by FIG. 2, it is clear that pins 16, 18, 20, 22 are embedded in the skeletal elements through the lateral surface of the middle 12 and distal 14 phalanges.
Despite the successful clinical record of devices like Hotchkiss"", there is room for improvement in the field. Many of the prior art devices and methods have potential problems and significant limitations that restrict their use in many applications. In particular, as shown in FIG. 2, Hotchkiss type devices 5 are required to be mounted on the lateral surface of the bones that extend from the contracted joint 10.
The Hotchkiss type device does not appear to be useable on metacarpal phalangeal (MP) joints. In the case of the proximal interphalangeal (PIP) joint 24, for example, a Hotchkiss type device 5 appears to be most useful for the second and fifth PIP joints. However, because other fingers of the hand, including the webbing, would interfere with installation and use of the device on the middle finger and ring finger PIP joints, an alternate solution is required. Further, with regard to all of the PIP joints, there are soft tissues and tendons that glide along the lateral and medial surfaces of the phalanges, particularly the proximal phalanges of the fingers, that can be impaled by pins inserted into the sides of these phalanges, as required in Hotchkiss type devices used on the PIP joints. Additionally, installation of a Hotchkiss type device on the second and third DIP joints 10 would require the fingers to remain partially spread throughout the treatment period. The Hotchkiss device is depicted as applied to the DIP distal joint of the finger, however, this device and others including variations of the subject invention often are applied to the PIP joints of the fingers. With application of such devices to either the DIP or PIP joints, device portions mounted on the lateral and medial aspects of the finger or extending therefrom are troublesome as they impinge the adjacent fingers.
In light of such prior devices, what is needed is a means for biasing contracted joints that can be used on many different joints. What is further needed is a device that is not restricted to use only where it can be mounted on the lateral surface of the bones extending from a contracted joint. It would further be beneficial to identify a way to apply force directly to the skeleton without detrimentally disrupting soft tissue and tendons on the lateral surface of the bones extending from the joint. Such a device would preferably permit simultaneous treatment of joints of adjacent fingers.
In splinting techniques used in hand surgery and hand therapy, if a splint uses a single elastic element that crosses more than one joint to treat contracture of one or both joints, it is impossible to balance the torques applied to each of the joints. Thus, what is needed is a device or means which simultaneously applies independent, controlled torque to multiple contracted joints that are adjacent along an appendage such as a finger.
The above and other deficiencies and problems with the prior art are addressed by the present invention of a multiple contracted joint biasing apparatus and method. The inventive, apparatus crosses and selectively controls torque forces applied to each skeletal joint in axial series, specifically when a first joint is proximal or distal to another. When applied to the hand, a first adjustable joint biasing torque apparatus may be surgically attached to the dorsal surface of the middle phalanx of a finger. This first adjustable joint biasing torque apparatus may be linked to a second proximal adjustable biasing torque apparatus by a rigid linkage. The second proximal adjustable biasing torque apparatus is positioned relative to the flexion-extension axis of the proximal joint by a removable brace that extends from the forearm across the wrist to cradle or embrace the hand.
More generally, a first adjustably biased mechanical joint is positioned on the extension side of a first contracted skeletal joint. A distal member extends from the first mechanical joint and is surgically attached to the bone extending from the contracted skeletal joint. A rigid linkage extends from the first mechanical joint and is attached to a second adjustably biased mechanical joint. A proximal member extends from the second mechanical joint and is removably attached to the appendage that extends proximally from the second contracted skeletal joint.
The first adjustably biased mechanical joint is operable to rotate with the same degrees of freedom as a normal, non-contracted skeletal joint of the same type as the first contracted skeletal joint. The adjustable biasing torque is applied to the skeletal joint via the distal member in the rotational direction of the desired range of skeletal joint motion. The second mechanical joint is positioned on the exterior side of a second contracted skeletal joint which is adjacent along the appendage that extends from the first skeletal joint. The second mechanical joint is operable to rotate with the same degrees of freedom as a normal, non-contracted joint of the same type as the second contracted joint. As with the adjustable biasing torque applied to the first skeletal joint by the first mechanical joint, the adjustable biasing torque for the second mechanical joint is applied to the second skeletal joint via the proximal member in the rotational direction of the desired range of motion for the second skeletal joint.
The adjustably biased mechanical joints of the apparatus are positioned so that they do not interfere with full extension of the patient""s skeletal joints. They are held in place by the attachments to the patient such that their respective biasing torques are independent of each other and their center of rotation is coincident or substantially coincident with the center of rotation of their associated skeletal joints.
The invention as applied to the MP and PIP joints of the fingers of the hand may include a wrist brace provided as a mounting point, as a means to hold the hand in position relative to the apparatus, and as a means to distribute the corrective force over a large area. In another variation, a proximal coupling plate serves as the proximal structural attachment to the hand. The wrist brace may be structurally stabilized by a fixation pin, such as a K-wire, which is attached to a bone of the hand or wrist, such as a metacarpal bone. The invention may be applied to more than one finger of the hand and up to all four finger MP and all four finger PIP joints. A xe2x80x9cUxe2x80x9d shaped transverse member is positioned over the dorsal surface of the brace and is pivotally attached to the distal end on the ulnar and radial sides of the brace. The ends of the xe2x80x9cUxe2x80x9d shaped transverse member are positioned such that a transverse line between them generally passes through the flexion and extension axes of rotation of the MP joints. In one variation, the xe2x80x9cUxe2x80x9d shaped transverse member may be replaced by a flexible tension element, preferably a cable or string, configured to couple the brace or proximal coupling plate with the more distal components.
Positioned dorsally above the PIP joint is an adjustably biased mechanical PIP joint. The mechanical PIP joint includes two members. The first member is an arcuate track that has an arc shaped track on its dorsal surface. The other is a slider block which engages and slides along the arcuate track member. The arcuate track member is mounted to the middle phalanx of the subject finger in such a way that the projected center of the arc is coincident or substantially coincident with the axis of rotation of the PIP Joint. Two fixation pins are drilled into the dorsal surface of the middle phalanx and the arcuate track member is secured to these pins. An adjustment means is provided to facilitate positioning the center point of the arc coincident or substantially coincident with the axis of rotation of the PIP joint.
A linkage may rigidly connect the slider block to the xe2x80x9cUxe2x80x9d shaped transverse member. The proximal end of this linkage may be attached to the xe2x80x9cUxe2x80x9d shaped transverse member through another swivel joint. The distal end of the linkage is attached to the slider block through a pin axis joint. The linkage allows the finger simultaneously to deviate in the radial and ulnar direction and to rotate through its normal range of motion during finger extension and flexion. An adjustment means is added to the length of this linkage to permit the apparatus to accommodate different hand sizes.
Thus, important aspects of the invention include a method and apparatus for applying torques to adjacent contracted joints along an appendage for the purpose of manipulating the joints to increase their range of motion. The invention incorporates the following principles:
(a) The axis of rotation of the applied torque is coincident or substantially coincident with the axis of rotation of the joint on which the torque is acting;
(b) The magnitude and direction of the torque applied to adjacent joints along an appendage can be controlled independently;
(c) The torque may be applied to the joint through a structure mounted directly to the skeleton or indirectly to the skeleton through a skin-preserving structure;
(d) The magnitude and direction of the torques applied to laterally neighboring joints, for example, joints of adjacent fingers on the same hand, can be controlled independently;
(e) The force required to leverage or counteract the torque to the most proximal joint may be applied to a brace-like structure that distributes the force over a large surface of the appendage or to proximal coupling plates which distribute forces directly to the skeleton of the hand.
An embodiment of the invention for the MP and PIP joints includes a means or device to allow the finger simultaneously to deviate in the radial and ulnar direction and to rotate through its normal range of motion during finger extension and flexion. This is achieved by connecting the part of the apparatus that is fixed to the middle phalanx of the finger to the remainder of the apparatus using a rigid linkage. The rigid linkage allows the part of the apparatus connected to the finger to move with the finger and to not restrict the movement of the finger in all of the normal planes of motion including that of MP flexion and extension where control is required.
The apparatus for this embodiment of the invention includes a force generating member such as a torsion spring, elastic band, servo-electrical, servo-hydraulic, coil compression or extension spring or the like; an apparatus that has a rotational movement where the axis of rotation of the device can be placed coincident or substantially coincident with the axis of rotation of a particular finger joint; and a means for attaching the force generating member to the apparatus that has a rotational movement such that the force is converted into a torque that acts about the center of rotation of the rotational apparatus.
Without the force generating members attached, the skeletal joints remain free to flex or extend and the fingers are free to deviate from side to side at MP joint level. If a force generating member is attached to only one of the mechanical joints of the apparatus, the other mechanical joint of the apparatus remains free to flex or extend without application of a biasing load. Thus, the mechanical joints of the apparatus are truly independent of each other and the torque generated by one mechanical joint of the apparatus is truly independent of any torque produced by the other.